Simultaneous production of magnesium and low carbon ferroalloys



Patented Apr. 1, 1941 SIMULTANEOUS PRODUCTION OF MAGNE- SIUM AND LOW CARBON FEKROALLOYS Ernst A. Pokorny, London, England, assignor to "ElectrometaP Societe Anonyme, of Luxemburg No Drawing. Application November 13, 1939,

Serial No. 304,153

4 Claims.

It is known that the oxyde of magnesium can be reduced by silicon or carbon or else by compounds of silicon or carbon such as s'ilicides or carbides respectively under conditions to yield metallic magnesium. The/reaction requires temperatures of more than 1200 centigrades and must take place in vacuum or in a reducing atmosphere.

Under these conditions of working the question of apparatus and the building material used is very diflicult to solve.

when working in the molten state, temperatures of more than 1700 centigrades are required for melting and even then the degree of liquidity obtained is not yet satisfactory for continuous technical working, because the slags containing oxyde of magnesium are, it is known, hard to liquefy.

On the other hand, when working in a sphere of temperatures at which the reacting materials are not yet molten, the reaction requires still temperatures of at least 1250 centigrades. As

the reacting materials must not come into cone,

tactwith the combustion gases, but, on the other hand, internal heating by metallic or carbon resistance is not applicable because the heaters are destroyed by the metallic vapors, it is necessary to work in enclosed reaction chambers heated from outside. This, however, puts a maximum strain on the constructing materials in question,

so that the wear of the apparatus is very great, which in turn greatly increases the production cost by repairs required.

In order to render the process economical it is,

therefore, necessary to modify it in a manner that by-products of high value can be obtained, the utilisation of which covers part of the cost.

Object of the present application is a process which allows the simultaneous production 'of magnesium metal and ferroalloys, low in carbon, as for instance. ferro-chromium, ferro-manganese etc. It has been ascertained by thorough experiments that neither manganese nor chromium react with the oxyde of magnesium at the temperature in question. Thus the reduction of the oxyde of magnesium by silicon, as such known, can be carried out in a manner that allows'the utilisation of alloys of ferro-chromiumsilicon, ferro-manganese-silicon etc. as reducing agents. It is known that carbon in alloys of l.

retro-chromium and ferro-manganese is displaced by silicon so f. i. an alloy containing about 30% of silicon does,not contain more than, at most, 0.5% of carbon. The same is true in the case of ferro-manganese.

The working process of utilisation of ferrochromium-silicon or ferro-manganese-silicon as reducing agents is as follows: oxyde of magnesi furnace, heated from outside, which may also be constructed as a rotary furnace. Alternatively the furnace can also be an electric arcor tubeor -muille-furnace fitted with electrical internal heaters -'(graphite or carbon resistance).

As soon as the reaction is "finished and the magnesium-metal-vapours formed, havebeen removed from the reaction chamber or have condensed in it, the residue is removed from the furnace and is molten by adding suitable fluxes in an electric furnace, the. slags formed are poured away after having separated from metal, and the metal, still containing some percent of silicon is refined as required. The ferro-chromium orferro-manganese of low carbon and silicon contents thus obtained represents a marketable I product of high value.

The reduction of the oxyde of magnesium by silicon can be carried out also in an electric arc furnace allowing to heat the mixture by radiating heat up to the temperature of reduction. In this case, after the reduction has been completed, the residue of the reaction is heated directly by means of the arc, adding fluxes such as silica, fluorspar etc. if necessary. The residue melts and by this the ferro-chromium or the ferromanganese is separated from the slags.

.The process may also be carried out in a high frequency furnace working with the silicon containing ferroalloy in a molten state.

Instead of ferro-chromium-silicon or ferromanganese-silicon also other alloys may be used in the same manner.

The residue of the reaction can be subjected to a mechanical or electromagnetic process of separation in order to obtainthe ferroalloy separate from the other components.

Having now particularly describedand ascertained the nature of the said invention and in what manner the same is to be performed I declare that what I claim is:

1. A process for the recovery of a binary ferroalloy and of magnesium from a ternary Ierro silicon alloy and a magnesia containing material which process comprises the steps oi reacting the magnesia containing material with aternary terro silicon 'alloy selected from the group consisting of ferro man'ganese-silicon' and termchromium-silicon, and removing the magnesium, and separating the binary Ierroalloy from the silica containing slag. J

a 1 2. A process as claimed in claim 1, in which the 

